This device relates to devices for measuring the level of refrigerant in a refrigeration system, and more particularly, to a device for indicating loss of the refrigerant and for automatically recharging the system.
A common problem relating to refrigeration systems is the determination of the correct amount of refrigerant in the system. Prior to starting the refrigeration system, the proper amount of refrigerant can sometimes be placed in the system by weighing the refrigerant. This method will work if the system's configuration is known precisely, including the length and size of all the lines in the system. In many systems, for example, home air conditioning systems with self-contained or remote units, these parameters are not known and would be cumbersome to measure. Therefore, a more direct method is needed to determine whether the correct amount of refrigerant is present in the system.
Another problem results from the loss of refrigerant from a system after the system is in operation. For example, a leak may develop which causes refrigerant to escape from the system. The refrigerant leak in a refrigeration system may be exiguous and slow in its loss of refrigerant. In such situations, the system may continue to operate for many weeks or months having an insufficient amount of refrigerant. When the system becomes low in refrigerant, the compressor continues to run with increasing duration, as the compressor must operate longer to compensate for the lack of refrigerant. The increased running of the compressor results in more electrical energy being used, and, in water-cooled systems, more water being used. In some cases, the stress placed upon the compressor can cause the motor to break down the oil and contaminate the entire system, thus necessitating expensive repairs if not component replacement.
Devices for measuring the level of liquids are known. For example, G. L. Koester U.S. Pat. No. 4,087,706 relates to a controller which uses a float as a contact with a pair of electrodes for controlling a liquid level.
Devices and systems for measuring quantities of refrigerant in a refrigerant system and recharging the system are also known. J. G. Nigro U.S. Pat. No. 2,893,217 describes a device for measuring the amount of refrigerant in the receiver of a refrigeration system. To function properly, the valve shown in Nigro must be located at the level of the receiver, and hence is restricted to those refrigeration systems having receivers. The Nigro patent also discloses the use of an automatic refrigerant charging system. Johnson et al U.S. Pat. No. 3,400,552 and Lamp et al U.S. Pat. No. 3,826,104 also disclose automatic charging systems for refrigeration units.
Arf U.S. Pat. No. 2,689,463 discloses an automatic refrigerant charging systems which uses a meter to control the amount of refrigerant being introduced into the refrigerating system. J. J. Talbot U.S. Pat. No. 3,729,949, R. A. Johnson U.S. Pat. No. 3,400,552 and Sarsten et al U.S. Pat. No. 3,668,882 relate to devices which measure the pressure and temperature of a refrigeration system and use these quantities to compute the amount of refrigerant in the system. These systems compute the amount of refrigerant using the perfect gas law or Van der Wall's equation, rather than directly measuring the quantity of refrigerant.
The Chiyoda U.S. Pat. No. 4,308,725 is a refrigerant quantity detecting device for the air conditioning of vehicles, and features a sensor utilizing a floating ball, with the arrangement being such that the sensing means has resistance to shocks and vibrations. However, the Chiyoda device is clearly limited to installation in the receiver of an air conditioning system, which imposes a definite limit as to the applicability of that invention inasmuch as in many refrigeration systems, no receiver is used. Instances of this include a capillary tube system and a cascade system. Also, the Chiyoda sensor is unable to provide an indication of the filter/dryer of the liquid line being partially stopped up. In this latter instance the system is unable to function properly, but the Chiyoda device unfortunately would fail to show a shortage of refrigerant.
For a system with a vertical rise from condenser to evaporator, it is possible for the liquid refrigerant to partially vaporize before getting to the throttling device. However, the Chiyoda sensor, limited to use in the receiver, would not sense this situation.
It was to overcome the severe disadvantages of these prior art devices that the present invention was evolved.